This invention relates to a picture compression managing apparatus and a picture compression managing method used therefor and, in particular, to an apparatus for carrying out digital compression of picture data or audio data to store compressed picture data or compressed audio data in a disk or a memory.
In an apparatus for carrying out digital compression of picture data or audio data to store compressed picture data or compressed audio data in a disk or a memory, one of merits is high random accessibility to a desired scene.
In a moving picture compression method utilizing interframe predictive coding, a frame to be decompressed may be a product of predictive coding. In this event, a reference frame must be decompressed first.
In order to affix an index to a picture compressed by predictive coding, use is typically made of a technique of detecting a key frame obtained by intraframe coding, for example, an I picture (intra-coded picture) and allowing jumping to the key frame. This technique is disclosed, for example, in Japanese Unexamined Patent Publication (A) No. H09-200772.
In the technique described in the above-referenced publication, a picture extracting section and a picture reducing section are provided. Specifically, a video bit stream is obtained by interframe compression, including periodical intraframe compression, as in the MPEG (Moving Picture Experts Group) system. The video bit stream is decoded by the use of a variable-length decoder, a dequantizer, an inverse DCT (Discrete Cosine Transform) unit, and so on. In this event, the picture extracting section extracts an intraframe compressed scene, i.e., an I picture from the video bit stream. The picture reducing section reduces the I picture thus extracted to produce a reduced picture. The reduced picture is written in a frame memory. Thus, multi-picture or multi-scene display is enabled and search is facilitated with a reduced scene used as an index.
In the existing technique mentioned above, the keyframe obtained by intraframe coding, for example, the I picture is detected and jumping to the key frame is allowed. Accordingly, the frame to which the index can be added is fixed or restricted.